A hybrid laser comprising a semiconductor pump laser and small-cavity rare earth fiber laser where laser cavities of both lasers are butt coupled or otherwise optically coupled to form a plurality of laser cavities that produce a plurality of emission wavelengths, one which may be the pump laser emission wavelength at the output of the fiber laser thereby forming a multi-wavelength combined output. The wavelengths in such an output may substantially match distinguishing spectral characteristic features along at least a portion of a characteristic optical spectrum of the analyte under examination providing a method of determining the concentration of an analyte in a specimen undergoing examination.